The aim of this study was to enroll a sibling of identical twins with IDDM who is at very high risk to develop IDDM (predicted time to develop IDDM 1.3 years) into a pilot study of the effect of intravenous and/or subcutaneous insulin on the development of diabetes. This study is being performed in conjunction with the Barbara Davis Center in Denver, Colorado, and the Joslin Clinic in Boston. Subject entered study in 10/94. As of 2/95, she has been receiving daily injections of insulin without signs or symptoms of IDDM.